In this study, we have examined the effect of polar jet and Bermuda High on ozone air quality in the eastern United States. In the Midwest and northeast, the poleward shift of jet wind leads to reduced polar jet frequency, resulting in increased ozone there. In the southeast, the influence of Bermuda High on ozone variability depends on the location of its west edge. Westward movement increases the ozone only when the JJA Bermuda High west edge is located west of 85.4°W.
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In this manuscript, we investigate the exchange of air masses across the dynamical tropopause (stratosphere-troposphere exchange, STE) in the vicinity of North Atlantic cyclones. By using two 6-hourly resolved ERA-Interim climatologies of STE and cyclones from 1979 to 2011, we are able to directly compute the amount of STE in the vicinity of every individual cyclone in this time period. This enables us to provide a robust and consistent quantification of STE near North Atlantic cyclones.
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The impact of aerosols on cloud cover (CC) under the influence of water vapor is studied using a decade of satellite observations. Water vapor is found to have a stronger impact on CC than aerosols. The water vapor impact shows that the hydrological cycle interferes with the aerosol climatic impact, and we need to improve our understanding of this interference.
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GROMOS (GROund-based Millimeter-wave Ozone Spectrometer) has provided ozone profiles for the NDACC (Network for the Detection of Atmospheric Composition Change) at Bern since 1994. We performed a trend analysis of our 20-year time series of stratospheric ozone profiles with a multilinear parametric trend estimation method. With our estimated ozone trends we are able to support the stratospheric ozone turnaround, besides a statistically significant negative trend in the lower mesosphere.
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On-road measurement of black carbon (BC), NOx and particle number (PN) emission factors (EF) by chasing vehicles is the first such study where BC EFs of many individual diesel cars were determined in real-world conditions. Median BC EF of diesel and gasoline cars in use for <5 years, decreased by 60% and 47% from those in use for 5–10 years. Reductions for goods vehicles' NOx and PN EFs were 52% and 67%. We found an increase of BC EFs in newer goods vehicle fleet compared to 5 – 10 year old one.
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We have developed an inorganic sea spray source function that is based upon state-of-the-art measurements of sea spray aerosol production using a temperature-controlled plunging jet sea spray aerosol chamber. The sea spray source function was implemented in a Lagrangian particle dispersion model and showed good skill in predicting measurements of Na+ concentration at a number of field sites, underlining its validity.
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In June and July 2013 dual-wavelength lidar measurements were performed in Barbados to study long-range transported Saharan dust across the Atlantic Ocean and investigate transport-induced changes. The focus of our measurements is the intensive optical properties, the lidar ratio and the particle linear depolarization ratio. While the lidar ratio shows no differences compared to the values of fresh Saharan dust, the particle linear depolarization ratio shows slight differences.
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SOA formations from vehicle exhausts and gas evaporation contribute 40% and 60% of total organic aerosols observed in summer and winter in urban Shanghai. Diesel vehicles, which accounted for less than 20% of vehicle kilometers of travel, contribute the most to vehicular POA emissions and SOA production in urban Shanghai. Intermediate-volatile organic compounds (IVOCs) in vehicle exhausts contribute greatly to SOA formation in the urban atmosphere of China.
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Combinations of simple mathematical model shapes called ellipsoids are used in many remote sensing and modeling applications to denote dust particles. In this study we investigate how accurately various physical parameters can be retrieved by using ellipsoids. The results show that using ellipsoids can lead to wrong results, while at the same time seeming like they work well. This means that extreme care should be used when using ellipsoids for dust, and extra validation measures should be used.
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We demonstrate that the current two-step approach to infer the CO2 surface fluxes from satellite measured radiances, with CO2 retrievals as an intermediate product, is not optimal. This suboptimality corrupts the 4D information flow from the radiance measurements to the surface flux estimates. It is amplified by current retrieval strategies where prior errors are much larger than the performance of prior CO2 simulations used in atmospheric inversions.
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We present a detailed analysis of a new greenhouse gas measurement network
in the Swiss Plateau, situated between the Jura mountains and the Alps. We
find the network's measurements to be information rich and suitable
for studying surface carbon fluxes of the study region. However, we are
limited by the high-resolution (2km) atmospheric transport model's ability
to simulate meteorology at the individual measurement stations, especially
at those situated in rough terrain.
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It is crucial for studying regional-scale PM pollution and for the development of efficient joint control policy to improve understanding of the regional background PM concentration. Based on the vertical variation periodic characteristics of particle mass concentration, the atmospheric boundary layer structure, as well as the vertical distribution of chemical composition and pollution source apportionment, a method to estimate regional background PM concentration is proposed.
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In this field study at Dome C, Antarctica, we investigated the effect of solar UV photolysis on the stable isotopes of nitrate in snow via comparison of two identical snow pits while exposing only one to solar UV. From the difference between the average isotopic fractionations calculated for each pit, we determined a purely photolytic nitrogen isotopic fractionation of -55.8‰, in good agreement with what has been recently determined in a laboratory study.
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Hydroxynitrates from isoprene oxidation were quantified both in the laboratory and through field studies. The yield of hydroxynitrates 9(+4/-3)% derived from chamber experiments was applied in a zero-dimensional model to simulate the production and loss of isoprene hydroxynitrates in an ambient environment during the 2013 Southern Oxidant and Aerosol Study (SOAS). NOx was determined to be the limiting factor for the formation of isoprene hydroxynitrates during SOAS.
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Pure MgCl2 particles and NaCl-MgCl2 mixed particles are systematically investigated to observe their hygroscopic behavior, derive experimental phase diagrams, and obtain chemical micro-structures. This work provides new interesting revelations regarding the efflorescence of MgCl2 hydrates during dehydration and also humidification. The observation of an aqueous phase over a wider RH range for NaCl-MgCl2 mixture particles indicates their more probable heterogeneous chemistry than NaCl particles.
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Trace element measurements in three particle size ranges (PM10-2.5, PM2.5-1.0 and PM1.0-0.3) were performed with 2h time resolution at kerbside, urban background and rural sites during the ClearfLo winter 2012 campaign in London. The environment-dependent variability of emissions was characterized using the Multilinear Engine implementation of the positive matrix factorization model. A total of nine different factors were resolved from local, regional and natural origin.
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This work highlights the important contribution of organic aerosols to the composition of submicron particles at remote mountain sites. Moreover, it confirms the importance of regional-scale physical and chemical processes and of transboundary transport in determining the background aerosol composition at rural European sites.
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Sea salt aerosols (SSA) are dominant particles in the Arctic atmosphere. Our result suggests that the hydrophilic MgCl2 coating in fresh SSA likely intrigued the heterogeneous reactions at the beginning of SSA and acidic gases in the Arctic. The content of organic matter increased in the aged SSA compared with the fresh SSA, which suggests organic acids (beside inorganic acids) participate in the ageing of SSA in the Arctic.
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The concentration and chemical composition of fine particulate matter were measured during the summer of 2012 in two Greek cities, Patras and Athens. The composition of PM1 was surprisingly similar in both areas, demonstrating the importance of regional sources. Analysis of the Aerosol Mass Spectrometer data suggested that the contribution of the primary sources to organic aerosol was important (22% in Patras and 35% in Athens) but not dominant.
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This manuscript presents the first long-term (14-month) and highly time-resolved (10 min) measurements of NR-PM1 aerosol chemical composition at a high-altitude site (JFJ, Switzerland, 3580m a.s.l.). The elevated location allowed the investigation of free tropospheric aerosol year round. Total and relative mass loadings, diurnal variations as well as seasonal variations are discussed together with geographical origin, organic aerosol sources and the influence of the planetary boundary layer.
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We measured condensation particle (CP) concentrations and particle size distributions at the coastal Antarctic station Neumayer. Several nucleation events were observed, but particles did not grow up to sizes required for acting as cloud condensation nuclei. A simple estimation indicated that apart from sulfuric acid, the derived growth rates required other low volatile precursor vapours.
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This paper provides monthly emission grid maps at 0.1deg x 0.1deg resolution with global coverage for air pollutants and aerosols anthropogenic emissions in 2008 and 2010.
Countries are consistently inter-compared with sector-specific implied emission factors, per capita emissions and emissions per unit of GDP.
The emission grid maps compose the reference emissions data set for the community modelling hemispheric transport of air pollution (HTAP).
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